2.1 Cancer
Cancer is one of the most significant health conditions. In the United States, cancer is second only to heart disease in mortality accounting for one of four deaths. The incidence of cancer is widely expected to increase as the US population ages, further augmenting the impact of this condition.
The current treatment regimens for cancer established in the 1970s and 1980s, have not changed dramatically. These treatments, which include chemotherapy, radiation and other modalities including newer targeted therapies, have shown limited overall survival benefit when utilized in most advanced stage common cancers since, among other things, these therapies primarily target tumor bulk.
Standard oncology regimens have often been largely designed to administer the highest dose of irradiation or a chemotherapeutic agent without undue toxicity, i.e., often referred to as the “maximum tolerated dose” (MTD) or “no observed adverse effect level” (NOAEL). Many conventional cancer chemotherapies and conventional irradiation therapies exert their toxic effects on cancer cells largely by interfering with cellular mechanisms involved in cell growth and DNA replication. Chemotherapy protocols also often involve administration of a combination of chemotherapeutic agents in an attempt to increase the efficacy of treatment. Despite the availability of a large variety of chemotherapeutic agents, these therapies have many drawbacks. For example, chemotherapeutic agents are notoriously toxic due to non-specific side effects on fast-growing cells whether normal or malignant; e.g. chemotherapeutic agents cause significant, and often dangerous, side effects, including bone marrow depression, immunosuppression, and gastrointestinal distress, etc.
Other types of traditional cancer therapies include surgery, hormonal therapy, immunotherapy, anti-angiogenesis therapy, targeted therapy, and radiation treatment to eradicate neoplastic cells in a patient. All of these approaches can pose significant drawbacks for the patient including a lack of efficacy and toxicity. Accordingly, new therapies for improving the long-term prospect of cancer patients are needed.
2.2 Non-Neoplastic Conditions
Angiogenesis is implicated in the pathogenesis of a variety of non-neoplastic conditions, e.g., intraocular neovascular syndromes such as proliferative retinopathies or age-related macular degeneration (AMD), rheumatoid arthritis, and psoriasis.
The recognition of VEGF as a primary stimulus of angiogenesis in pathological conditions has led to various attempts to block VEGF activity. Inhibitory anti-VEGF receptor antibodies, soluble receptor constructs, antisense strategies, RNA aptamers against VEGF and low molecular weight VEGF receptor tyrosine kinase (RTK) inhibitors have all been proposed for use in interfering with VEGF signaling (Siemeister et al. (1998) Cancer Metastasis Rev., 17(2):241-248). However, these agents all have drawbacks in that they can cause toxic side effects in the patient and often are not curative of the non-neoplastic condition. Accordingly, new therapies for treating patients with non-neoplastic conditions that are associated with angiogenesis, particularly VEGF production, are needed.
2.3 Viral Conditions
As obligate intracellular parasites, viruses are intimately dependent upon the biological functions of their hosts. Small molecules that affect the host cell biological processes involved in viral replication or the production of viral RNA or DNA or viral protein may therefore inhibit a wide variety of viruses requiring these functions for essential events in the viral life cycle and therefore can be used for treatment of virus infection. Notably, molecules directly affecting host functions that are essential for viral replication or the production of viral RNA or DNA or viral protein should provide a high barrier to the emergence of resistant strains relative to classical antivirals that directly target viral enzymes.
An estimated 170 million people worldwide are reported to be infected with hepatitis C virus, of which at least 6 known genotypes are the causative agent of hepatitis C infection. Up to 80 percent of HCV infections lead to chronic liver infection, which in turn may result in severe liver diseases, including liver fibrosis, cirrhosis, and hepatocellular carcinoma (see Saito I, et al., Hepatitis C virus infection is associated with the development of hepatocellular carcinoma, Proc Natl Acad Sci USA, 1990, 87:6547-6549). References have described small molecule β-carboline compounds with antiviral activity against viruses such as human papillomavirus (HPV) (J F Miller et al, Bioorganic & Medicinal Chemistry Letters, 2010, 20(1):256-259), poliovirus (PV) and herpes simplex virus (ASN Formagio et al, European Journal of Medicinal Chemistry, 2009, 44(11):4695-4701). International Patent publications WO2006/015035 and WO2007/002051 describe β-carboline compounds with antiviral activity against human papillomavirus infection (HPV) and a flavivirus infections, including dengue virus, yellow fever virus, West Nile virus and hepatitis C virus (HCV) infection. Accordingly, new small molecule therapies for treating patients with viral conditions, particularly dengue virus and HCV, are needed.